Field of the Invention
This invention relates to an improved call pacing method for a call center outbound automatic dialing function and more particularly to a pacing method capable of holding to low set abandon rates.
U.S. Pat. No. 5,640,445, which is incorporated herein by reference, discloses a call pacing method in which agent availability and call answers are based on probability statistics. For the agent availability determination, a weight is assigned each agent engaged in a call or in after-call work. This weight is a function of how long an agent has been engaged in a call or in after-call work and the length of an adjustable time window. The sum of the weights is a predicted number of engaged agents that will become free. The length of the time window, which is typically not the same for agents engaged in a call and agents engaged in after-call work, is not explicitly dependent on the interval between the dial of a call and when the call is expected to be answered. The time window is adjusted by the system; lengthened when the abandon call rate falls below the maximum acceptable ratio (herein referred to as the set abandon rate) and shortened when the set abandon rate rises above the set abandon rate.
Calls to be dialed may be separated into classes based on the probability that a dialed call will be answered (e.g. previously dialed, busy responses will have a higher probability of answer than a previously dialed no answer response). Separate data of answer vs. dials are kept for each class. Dialed calls that remain unanswered are further discounted as the unanswered status extends in time and the data indicates a diminished probability of being answered.
For each class, a number of calls to dial is calculated, based on the probability of an answer, in order to provide answered calls for the predicted number of idle agents without the predicted number of abandons exceeding the allowable or set abandon rate (as used herein, the phrase "predicted idle agents" includes engaged agents predicted to become available plus presently idle agents). Calls to dial are calculated from the various classes, starting with the class with the highest probability of an answer, so that the fewest dials are used to produce the required number of answered calls. For each class, the calculation of the number of calls to dial is based on an assumed binomial distribution of the likelihood of a given number of answers if the predicted number of idle agents divided by class answer probability is less than a predetermined number; if larger than this number a normal distribution is used for ease of calculation.
The pacing method of the U.S. Pat. No. 5,640,445 patent gains a significant performance advantage by estimating the proportion of ringing dials that will not result in an answer. It then begins dialing new calls to substitute for these calls. It uses an "average" estimation calculation for the number of ringing dials which will not answer, which is adequate for abandon rates in the neighborhood of 5.0 percent, but has not been altogether satisfactory for very low set abandon rates, e.g., 0.5 percent. This is because with a low set abandon rate, there is very little room for the errors ("error distribution") that an "average" estimator will usually produce. Low set abandon rates of 0.5 percent involve at most one abandoned call for every 200 answers, in contrast to one abandoned call for every 20 answers for the higher rate of 5.0 percent.
Prior art pacing methods, including the U.S. Pat. No. 5,640,445 pacing method, use only an "after-the-fact" control mechanism; that is, the method slows down the rate of dialing once the set abandon rate is exceeded. However, due to the very small margin for error with low set abandon rates, this "after the fact" mechanism is not satisfactory. This same "after the fact" mechanism is also used to speed up the dialing, if the abandon rate is too low, which can also cause unwanted effects for low set abandon rates.
An object of this invention is to provide an improved pacing algorithm which precisely maintains a set abandon rate, even low set abandon rates and even in an environment where the talk time is long.
Briefly this invention contemplates the provision of a "look-ahead" calculation, that projects what would be the effect on the abandon rate if several additional abandons happened to occur. This could be characterized as estimating the abandon rate sensitivity. The method uses the result of this "look-ahead" calculation of a projected abandon rate to modify its estimation of the number of ringing dials that will or will not result in an answer. If the projected abandon rate indicates the abandon rate is sensitive to an increase in the number of abandons, the method increases the estimate of those ringing calls which are likely to answer by up to two and one-half times the "average", depending on the degree of sensitivity. If the sensitivity forecasts little danger of exceeding the set abandon rate, the method decreases the estimate of ringing calls that will answer by up to one-half. In the former case, dialing is slowed down and in the latter, dialing is speeded up. Both cases have the advantage to "looking ahead" rather than simply reacting to events that may not be quickly correctable once they have occurred.
In a preferred embodiment, the method of this invention uses the mathematically-based Binomial algorithm of the U.S. Pat. No. 5,640,445 patent to estimate how many calls are safe to dial, which is most accurate when there are no or few dials ringing. When there are few dials ringing, the "look-ahead" calculation has little effect. In this case, the Binomial algorithm exercises the most control on the dialing rate, which is precisely when it is most accurate. When there are many dials in progress, the "look-ahead" calculation gains more control, as it should.